Peelable film for a medical packaging container

ABSTRACT

An easily peelable film comprising a mixture of a propylene/α-olefin copolymer (A), a propylene/α-olefin copolymer (B) having an α-olefin content different from that of the copolymer (A), and/or a propylene homopolymer (C). The easily peelable film has excellent heat resistance, flexibility, and transparency and further a broad temperature range for low temperature welding at which peelable partition walls can be formed.

[0001] This application is a division of application Ser. No.10/367,818, filed Feb. 19, 2003, which is a continuation of applicationSer. No. 09/731,781, filed Dec. 8, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates to films showing excellent easypeelability when the films are sealed to each other and medicalpackaging containers using the films as an inner layer.

[0003] Herein, the term “easy peelability” means that the following twoportions can be formed selectively from one material. They are astrongly heat welded portion that can be sealed by heating two membersof one material at a relatively high temperature and cannot besubstantially peeled, and a weakly heat welded portion that can besealed by heating the members of the material at a relatively lowtemperature (hereinafter referred to as low temperature welding) and canbe easily peeled.

BACKGROUND OF THE INVENTION

[0004] Hitherto, there have been known lid materials and packagingmaterials provided with an adhesive surface that can be easily peeled tofacilitate unsealing as well as medical multi-chamber containerspartitioned with easily peelable partition walls.

[0005] Medical multi-chamber containers are used for applications suchas the aseptical mixing, immediately before use, of drugs or chemicalsolutions that tend to be denatured or to have decreased preservativequalities when they are in a mixed state. That is, the contents arepreserved in a container separately in a plurality of chamberspartitioned by partition walls that can be easily peeled. The containeris compressed by hand immediately before use so as to have the chamberscommunicate with each other and have the contents aseptically mix.

[0006] The multi-chamber container is usually formed of a single layerfilm having easy peelability mentioned above or formed of a multi-layerfilm obtained by laminating the film having easy peelability as an innerlayer. First, a peripheral portion of superposed films is heat welded ata relatively high temperature to form a container. Then, an intermediateportion of the formed container is heat welded at a relatively lowtemperature from outside of the container using a heating mold in orderto form easily peelable partition walls and partition the container intoa plurality of chambers. Where the multi-chamber container is formed ofa resin that does not show easy peelability, the partition walls in themulti-chamber container can be formed by inserting an easily peelablefilm (usually, a film made of a mixture of the resin used for the filmfor forming the container and a resin incompatible therewith) betweenpartition wall portions and heat welding the partition wall portionstogether.

[0007] The easily peelable film used for the medical container mustsatisfy heat resistance, transparency, flexibility and impact resistancerequirements as well as medical safety requirements and disposabilityand thus far many proposals have been made.

[0008] For example, there have been known easily peelable films made ofmixtures of polypropylene type polymers and ethylene/α-olefin typeelastomers (JP-A-Hei 7-136234 and JP-A-Hei 8-131515) and films made ofmixtures of polypropylene type polymers or polyethylene type polymers asa major component and styrene type elastomers (JP-A-Hei 8-229099 andJP-A-Hei 8-229100). However, these films contain a large content of theα-olefin or the elastomer so that they have poor heat resistance and anincreased change or fluctuation in peel strength of the formed partitionwalls, allowing high pressure steam sterilization to be performed onlyat 115° C. or less.

[0009] On the other hand, easily peelable films made of resincompositions containing polyolefin type resins and incompatible resinssuch as polymethylpentene type resins having excellent heat resistance(JP-B-Hei 7-96283) have blended therein a significant amount ofincompatible resins so that they are poor in transparency andflexibility, and are unsuitable as medical containers.

[0010] Furthermore, a bag using a copolymer comprising an homogeneousphase of propylene for internal partition walls is also known (JP-A-Hei10-314275). The copolymer comprising an homogeneous phase of propylenepreferably has a melting point of 150-160° C. and contains about 3% byweight of an ethylene component. However, although a bag made of thecopolymer is excellent in heat resistance, a temperature range for lowtemperature welding at which peelable partition walls can be formed isas narrow as 137.50±1° C., so that it is difficult to form partitionwalls.

SUMMARY OF THE INVENTION

[0011] The present invention has been made in view of the abovecircumstances and an object of the present invention is to provide aneasily peelable film that has excellent heat resistance, flexibility,and transparency and further has a broad temperature range for lowtemperature welding at which peelable partition walls can be formed, anda medical packaging container using the above-mentioned film.

[0012] The present inventors have made intensive research to achieve theabove object and have discovered that use of a mixture of two or morepropylene polymers having different melting points can attain the aboveobject, thus achieving the present invention.

[0013] That is, the present invention relates to an easily peelable filmcomprising a mixture of a propylene/α-olefin copolymer (A) and apropylene/α-olefin copolymer (B) having an α-olefin content differentfrom that of the copolymer (A), and/or a propylene homopolymer (C).

[0014] Also, the present invention relates to an easily peelablelaminated film using the above-mentioned film as a surface layer film.

[0015] Furthermore, the present invention relates to a medical packagingcontainer using the easily peelable film or easily peelable laminatedfilm.

[0016] The propylene/α-olefin copolymer (A) according to the presentinvention has a melting point of 110-130° C., preferably 115-125° C. Onthe other hand, the propylene/α-olefin copolymer (B) according to thepresent invention has a melting point of 130-170° C., preferably135-155° C. The propylene homopolymer (C) according to the presentinvention has a melting point of 130-170° C., preferably 161-170° C.Where the melting point of (A) is lower than 110° C. or the meltingpoint of (B) or (C) is lower than 130° C., the film or packagingcontainer after molding has poor heat resistance, so that there is apossibility that a decrease in transparency or a deformation of thecontainer after high pressure steam sterilization can occur. Where themelting point of (A) is higher than 130° C., the difference from themelting point of (B) or (C) is small, so that it is difficult to formeasily peelable partition walls.

[0017] Furthermore, a difference between the melting point of (A) andthe melting point of (B) or (C) is preferably at least 5° C. and, morepreferably, 7° C. or more. If the difference in melting point is smallerthan 5° C., it is difficult to selectively form a strong heat weldedportion or a weak heat welded portion.

[0018] The melting point referred to herein means a temperature at whicha DSC (differential scanning calorimetry) measurement of the copolymeror homopolymer pellets gives a maximum endothermic peak by melting.

[0019] The α-olefin content of the propylene/α-olefin copolymer (A) is5-20 mol % and, preferably 7-15 mol %. The α-olefin content of thepropylene/α-olefin copolymer (B) is 8 mol % or less and, preferably, 7mol % or less. If the α-olefin content of the propylene/α-olefincopolymer (A) is higher than 20 mol %, not only are the heat resistanceand transparency decreased but also, the peel strength increases wheneasily peelable partition walls are prepared, so that it is difficult torelease the partition walls by hand.

[0020] The mixture that forms the easily peelable film according to thepresent invention may be a mixture of three components, i.e., thepropylene/α-olefin copolymer (A), propylene/α-olefin copolymer (B), andthe propylene homopolymer (C) or a mixture of two components, i.e., (A)and (B) or (A) and (C). Copolymer (A) may be two or morepropylene/α-olefin copolymers having a melting point of 110-130° C.Copolymer (B) maybe two or more propylene/α-olefin copolymers having amelting point of 130-170° C. and propylene homopolymer (C) may be two ormore propylene homopolymers.

[0021] As the α-olefin of the propylene/α-olefin copolymer (A),α-olefins having 2 or 4-8 carbon atoms and, more specifically, ethylene,butene, pentene, hexene, heptene, octene or two or more of these can beused. That is, specific examples of the propylene/α-olefin copolymer (A)according to the present invention can be, in addition to bipolymerssuch as propylene/ethylene copolymers, propylene/butene copolymers, andterpolymers such as propylene/ethylene/butene copolymers.

[0022] As the α-olefin of the propylene/α-olefin copolymer (B), the sameones as can be used in the propylene/α-olefin copolymer (A) can be used.Where the mixture forming the easily peelable film according to thepresent invention contains both (A) and (B), the α-olefins of (A) and(B) can be the same as long as their contents are different. Ifdifferent α-olefins are used, their contents can be the same ordifferent.

[0023] In the present invention, it is preferred that the α-olefin inthe above (A) or (B) is ethylene and, more preferably, the α-olefin inboth of the above (A) and (B) is ethylene.

[0024] A film formed of propylene/α-olefin copolymer (A) according tothe present invention preferably has a tensile modulus of 2,000-10,000kg/cm². A film formed of propylene/α-olefin copolymer (B) or propylenehomopolymer (C) preferably has a tensile modulus of 3,000-17,000 kg/cm².If the tensile modulus of copolymer (A) is smaller than 2,000 kg/cm² orthe tensile modulus of copolymer (B) or (C) is smaller than 3,000kg/cm², the film prepared from the mixture of copolymer (A) andcopolymer (B) and/or homopolymer (C) has insufficient strength and thereis a possibility that sticking between the surfaces of two-folded filmscould occur. If the tensile modulus of copolymer (A) is larger than10,000 kg/cm² or the tensile modulus of copolymer (B) or (C) is largerthan 17,000 kg/cm², there is a possibility that the film prepared fromthe mixture of copolymer (A) and copolymer (B) and/or homopolymer (C)has insufficient flexibility.

[0025] It is preferred that the mixing ratio of the propylene/α-olefincopolymer (A) to the propylene/α-olefin copolymer (B) and/or thepropylene homopolymer (C) is 15-85:85-15 by weight. If the amount ofpropylene/α-olefin copolymer (A) is less than 15% by weight and theamount of propylene/α-olefin copolymer (B) and/or the propylenehomopolymer (C) are/is more than 85% by weight, the peel strength ofpartition walls is too low when the easily peelable partition walls areformed of the prepared film, or the range of welding temperature atwhich the partition walls are formed is narrow. If the amount ofpropylene/α-olefin copolymer (A) is more than 85% by weight and theamount of propylene/α-olefin copolymer (B) and/or the propylenehomopolymer (C) are/is less than 15% by weight, conversely, the peelstrength of the partition walls is too high or there is a possibilitythat the film becomes sticky.

[0026] The easily peelable film according to the present invention canbe prepared by a conventional method from a mixture of thepropylene/α-olefin copolymer (A) and the propylene/α-olefin copolymer(B) and/or the propylene homopolymer (C). The method of mixing thepolymers is not particularly limited but it is preferable that the resinpellets are preliminarily dry blended or that they are melt blendedusing a double-screw extruder.

[0027] At the time of fabrication of the mixture according to thepresent invention into easily peelable films, conventionally knowningredients such as heat stabilizers, antioxidants, ultravioletabsorbents may be added thereto. A preferred amount of the ingredientsadded there to is 0.001-10% by weight based on the mixture. Insofar asthe properties of the easily peelable film according to the presentinvention are not adversely affected, thermoplastic resins such ascompatibilizers, lubricants, anti-blocking agents, antistatic agents,pigments, anti-microbial agents, etc. may be added. Known surfacetreatments such as ozone treatment, corona treatment, vapor depositiontreatment, etc. may also be carried out.

[0028] The easily peelable film according to the present invention maybe a laminated film comprising the easily peelable film as at least onesurface layer thereof and a layer of another resin laminated there on inorder to improve the gas barrier property, easy peelability, mechanicalproperties and the like. The other resin as used herein includesα-olefin type resins such as polypropylene type resins,propylene/α-olefin copolymers, polyethylene type resins,ethylene/α-olefin copolymers, polybutene and the like, cyclic polyolefintype resins, ethylene/vinyl alcohol copolymers, and ethylene/vinylacetate copolymers as well as thermoplastic resins such as polyamidetype resins and polyester type resins, or mixtures of these resins.

[0029] The easily peelable film according to the present invention canbe produced by methods similar to the molding method used for generalthermoplastic resins, such as T-die molding, inflation molding and thelike. The easily peelable laminated film can be produced by methods suchas co-extrusion molding, dry laminating and extrusive coating.

[0030] The easily peelable film obtained by the present invention has athickness of preferably about 5-500 μm and, more preferably, 2-400 μm.If the film is thinner than 5 μm, the strength of the film isinsufficient or it is difficult to form partition walls having excellenteasy peelability. If the film is thicker than 500 μm, the flexibility ofthe film is decreased and welding of the film is difficult.

[0031] Furthermore, the easily peelable laminated film according to thepresent invention has a thickness of 10-500 μm and, preferably 20-400μm. The ratio of the thickness of the film or films having easypeelability in a laminated film comprising one or more films having easypeelability and one or more films not having easy peelability is 0.05 ormore, preferably 0.10 or more, based on the total film thickness. If itis less than 0.5, the peel strength of the easily peelable partitionwalls formed of the film decreases.

[0032] The easily peelable film or easily peelable laminated filmaccording to the present invention may be used as it is as a lidmaterial for an easily peelable container, a sealing film for rubberstopper caps of an infusion bag or may be molded into medical packagingcontainers having easily peelable partition walls. Although thepackaging containers can be molded by heat welding the film, they canalso be produced directly from the above mixtures by blow molding,vacuum forming or like methods. The packaging containers includemulti-chamber containers, blister packs, etc.

[0033] Among the medical packaging containers according to the presentinvention, for example, multi-chamber containers can be obtained bywelding the central portion of a tubular film obtained by inflationmolding at a low temperature to form two chambers partitioned by theeasily peelable partition wall, filling the chambers with desiredcontents, and strongly heat welding the peripheral portion of thetubular film. Also, the above container can be obtained by forming thechambers partitioned by the easily peelable partition walls mentionedabove, then strongly heat welding the peripheral portion of the filmsuch that a mouth member for filling the contents is inserted in theperipheral portion of the film. Furthermore, the partition wall of thecontainer can also be formed by inserting the easily peelable film oreasily peelable laminated film according to the present inventionbetween portions to be a partition wall of a flexible container which isformed of a film not having easy peelability, and heat welding theinserted portions from outside the container.

[0034] In order to form easily peelable partition walls using the easilypeelable film or easily peelable laminated film according to the presentinvention, heat welding is performed at a temperature that is higherthan a melting point of the polymer having the lowest melting point andlower than the melting point of the polymer having the highest meltingpoint of the polymer mixture which forms the easily peelable film or ofthe film having easy peelability in the easily peelable laminated film.More particularly (depending on the components of the resin used,specification of the welding machine, and welding conditions), it ispreferred that the low temperature welding is performed at about130-150° C. As compared with the conventional low temperature weldingthat has been performed in a narrow temperature range such as 137.5±1°C., when easily peelable partition walls are formed using the filmaccording to the present invention, the temperature range issufficiently broad that molding failure of the easily peelable partitionwalls will hardly occur. Low temperature welding under the aboveconditions can produce easily peelable partition walls having a T-peelstrength (as measured by an Instron type universal tester or the likeusing strap-like test pieces such that the peel angle is 180°) of0.2-0.6 kg/15 mm (tension speed: 300 mm/minute). The multi-chambercontainer having the partition walls can be compressed by hand torelease, or break the partition walls and allow the plurality ofchambers to easily communicate with each other.

[0035] On the other hand, to form a peripheral portion of themulti-chamber container that is strongly heat welded, heat welding isperformed at a temperature higher than the melting point of the polymerof the mixture having the highest melting point. Specifically, it ispreferred that the strong heat welding is performed at 150-220° C.

[0036] As the method for heat welding, the same methods as those methodsused for welding ordinary olefin type thermoplastic resins such aswelding using a hot mold, supersonic welding and high frequency welding,can be used.

[0037] The multi-chamber container produced by the above method issubjected to high pressure steam sterilization usually at 110-121° C.after filling the contents in the chambers and sealing. The contents mayinclude not only fluids such as dialysis solutions for artificialkidneys, exchange solutions for filtration type artificial kidneys andinfusion preparations, but also powders, solids, etc. Theabove-described multi-chamber containers undergo no change in thereleasability of the easily peelable partition walls or transparency ofthe container even after sterilization at a temperature of 115° C. orhigher.

EXAMPLES

[0038] Hereinafter, the present invention will be described in moredetail by examples. However, the present invention is not limited to theexamples.

[0039] The resins used in the examples are shown below. The resins hadbeen molded into pellets before they were used.

[0040] PP-A: Propylene/ethylene copolymer

[0041] Ethylene content: 9 mol %

[0042] Tensile modulus: 3,400 kgf/cm²

[0043] Melting point: 121° C.

[0044] Melt flow rate (MFR) (210° C., 2.16 kgf): 2.5 g/10 minutes

[0045] PP-B: Propylene/ethylene copolymer

[0046] Ethylene content: 6 mol %

[0047] Tensile modulus: 5,000 kgf/cm²

[0048] Melting point: 143° C.

[0049] MFR (210° C., 2.16 kgf): 2.7 g/10 minutes

[0050] PP-C: Propylene homopolymer

[0051] Tensile modulus: 13,500 kgf/cm²

[0052] Melting point: 161° C.

[0053] MFR (210° C., 2.16 kgf): 9.0 g/10 minutes

Examples 1-4

[0054] Mixtures were prepared by dry blending PP-A and PP-B in a mixingratio by weight of2:1 (Example 1), 1:1 (Example 2), and 1:2 (Example 3)and PP-A and PP-C in a mixing ratio by weight of 2:1 (Example 4).

[0055] The obtained mixtures were molded into tubular films of 200 μm inthickness and of 200 mm in lay flat width (width of the tubular filmwhen folded flat) using a water cooled inflation film molding machine.The tubular films were cut into portions of a length of 300 mm. Eachportion was subjected to low temperature welding at the center across awidth of film of 15 mm at a pressure of 5.0 kg/cm² for 10 seconds atthree mold temperatures of 130° C., 140° C., and 150° C. to formpartition walls. In each of the chambers in the tubular films formed bythe partition walls 200 ml of distilled water was filled and the ends ofthe chambers were heat welded across a width of 10 mm at a pressure of 5kg/cm² for 10 seconds at a mold temperature of 180° C. to seal thetubular film, thus fabricating a multi-chamber container.

Comparative Examples 1 and 2

[0056] Multi-chamber containers made of a single layer film of PP-A(Comparative Example 1) and a single layer film of PP-B (ComparativeExample 2), respectively, were produced using the same procedures asdescribed in Examples 1-4.

[0057] Evaluation of Easily Peelable Films and Multi-Chambers

[0058] (a) Evaluation of Medical Safety

[0059] The films obtained in Examples 1-3 were subjected to tests onelutes based on the 13^(th) Revision of Japan Pharmacopoeia, standardsof plastic containers for medicines. As a result, all the films wereacceptable and showed that they had sufficient safety as medical films.

[0060] (b) Evaluation of Tensile Modulus

[0061] The films obtained in Examples 1-4 and Comparative Examples 1 and2 above were cut to mold dumbbell shaped specimens, which were measuredfor tensile modulus (JIS-K7127) using an Autograph tester (AG-500D,manufactured by Shimadzu Corporation). The results are shown in Table 1.

[0062] As will be apparent from Table 1, it is understood that the filmsaccording to the present invention and of the Comparative Examples hadsufficient flexibility for use in fabricating medical packagingcontainers.

[0063] (c) Evaluation of Light Transmittance

[0064] The multi-chamber containers obtained in Examples 1-4 andComparative Examples 1 and 2 above were subjected to high pressure steamsterilization at 121° C. under a pressure of 1.5 kg/cm² for 20 minutesand then to light transmittance at a wavelength of 450 nm in wateraccording to “Test methods for plastic made containers for medicines,”13^(th) Revision of Japan Pharmacopoeia using a spectrophotometer(U-3210,manufactured by Hitachi Ltd.) to evaluate the transparency ofthe films. The results are shown in Table 1.

[0065] As will be apparent from Table 1, each of the multi-chambercontainers of Examples 1-4 maintained transparency after the highpressure steam sterilization.

[0066] (d) Measurement of T-Peel Strength

[0067] The easily peelable partition wall portions of the multi-chambercontainers obtained in Examples 1-4 and Comparative Examples 1 and 2 andsubjected to the high pressure steam sterilization under theabove-described conditions were measured for peel strength by a 1800T-peel test at a film width of 15 mm at a test speed of 300 mm/minutesusing an Autograph tester (AG-500D, manufactured by ShimadzuCorporation). The results are shown in Table 1.

[0068] As will be apparent from Table 1, the multi-chamber containersusing the easily peelable films of Examples 1-4, regardless of beingwelded at a temperature of 130° C., 140° C. or 150°, had excellent peelstrength after the high temperature steam sterilization. However, themulti-chamber containers using the film of Comparative Example 1 hadhigh peel strength regardless of the temperature at which they were lowtemperature welded and the multi-chamber container using the film ofComparative Example 2 showed excellent peel strength only when it waslow temperature welded at 150° C., thus showing a narrow temperaturerange for low temperature welding. TABLE 1 Composition Tensile LightT-Peel strength (mixing ratio modulus trans-mittance (kgf/15 mm) byweight) (kgf/15 mm) (%) 130° C. 140° C. 150° C. Example 1PP-A(2)/PP-B(1) 1,200 75 0.58 0.60 0.50 Example 2 PP-A(1)/PP-B(1) 1,30077 0.27 0.36 0.38 Example 3 PP-A(1)/PP-B(2) 1,500 81 0.20 0.25 0.30Example 4 PP-A(2)/PP-C(1) 1,300 78 0.42 0.46 0.43 Comparative PP-A 1,00083 0.75 0.77 0.77 Example 1 Comparative PP-B 1,600 72 0.11 0.13 0.22Example 2

[0069] Advantageous Effects of the Invention

[0070] The easily peelable film according to the present invention is afilm made of a mixture of a propylene/α-olefin copolymer (A), apropylene/α-olefin copolymer (B) having an α-olefin content differentfrom that of the copolymer (A), and/or a propylene homopolymer (C) andcan be low temperature welded by utilizing a difference in melting pointtherebetween so that partition walls having excellent easy peelabilitycan be formed. Furthermore, the welding temperature range of the film isbroader than the conventional temperature range so that there is no fearof causing molding failure of easily peelable partition walls.Sterilization performed at a temperature as high as 115° C. or higherdoes not result in deterioration of transparency of the film or peelstrength of the easily peelable partition walls.

What is claimed is:
 1. A film for a medical packaging containercomprising a peelable film comprising 90% or more by weight of a mixtureof a propylene/α-olefin copolymer (A) and at least one of apropylene/α-olefin copolymer (B) having an α-olefin content differentfrom that of the copolymer (A) and a propylene homopolymer (C), whereinthe propylene/α-olefin copolymer (A) has an α-olefin content of 5-20 mol% and a melting point of 110-130° C., the propylene/α-olefin copolymer(B) has an α-olefin content of 8 mol % or less, the propylene/α-olefincopolymer (B) and the propylene homopolymer (C) each have a meltingpoint of 130-170° C., and a difference between the melting point of (A)and the melting point of (C) is each at least 5° C. and wherein theα-olefin in the propylene/α-olefin copolymer (A) and the α-olefin in thepropylene/α-olefin copolymer (B) are α-olefin having 2 or 4 to 8 carbonatoms.
 2. The film for a medical packaging container claimed in claim 1,wherein the film is tubular.
 3. The film for a medical packagingcontainer claimed in claim 1, wherein the film is a plain monolayerfilm.
 4. A laminated film for a medical packaging container comprising apeelable laminated film, wherein said peelable laminated film comprises,as a surface layer, a film comprising 90% or more by weight of a mixtureof a propylene/α-olefin copolymer (A) and at least one of apropylene/α-olefin copolymer (B) having an α-olefin content differentfrom that of the copolymer (A) and a propylene homopolymer (C), whereinthe propylene/α-olefin copolymer (A) has an α-olefin content of 5-20 mol% and a melting point of 110-130° C., the propylene/α-olefin copolymer(B) has an α-olefin content of 8 mol % or less, the propylene/α-olefincopolymer (B) and the propylene homopolymer (C) each have a meltingpoint of 130-170° C., and a difference between the melting point of (A)and the melting point of (C) is each at least 5° C. and wherein theα-olefin in the propylene/α-olefin copolymer (A) and the α-olefin in thepropylene/α-olefin copolymer (B) are α-olefin having 2 or 4 to 8 carbonatoms.
 5. The laminated film for a medical packaging container claimedin claim 4, wherein the laminated film is tubular.
 6. The laminated filmfor a medical packaging container claimed in claim 4, wherein thelaminated film is a plain multilayer film.
 7. The laminated film for amedical packaging container claimed in claim 4, wherein the laminatedfilm is a lid material for an easily peelable container.
 8. Thelaminated film for a medical packaging container claimed in claim 4,wherein the laminated film is a sealing film for rubber stopper caps ofan infusion bag.